This invention relates generally to electric-actuated fuel injectors that inject fuel into combustion chambers of internal combustion engines, and in particular to calibration group identifiers for such fuel injectors.
An electric-actuated fuel injector for a compression-ignition internal combustion engine may comprise an intensifier piston for creating a high pressure injection of fuel directly into an associated engine cylinder. An intensifier piston comprises a head of given end area exposed to a control fluid, oil for example, in a control chamber, and a plunger, or rod, of smaller end area exposed to liquid fuel in an injection chamber.
The fuel injector may comprise an electric-actuated spool valve for controlling both the introduction of pressurized control fluid into the control chamber and the draining of control fluid from the control chamber. When an electric signal for initiating a fuel injection is applied to an electric actuator of the spool valve, control fluid is introduced under pressure through one portion of the spool valve into the control chamber to downstroke the intensifier piston and cause fuel in the injection chamber to be injected under pressure from a nozzle of the fuel injector into an associated engine cylinder. The intensifier piston is effective to amplify the pressure of the control fluid by a factor equal to the ratio of the head end area to the plunger end area and cause the amplified pressure to be applied to liquid fuel in the injection chamber. As a result, fuel is injected into a combustion chamber at a pressure substantially greater than the pressure of the control fluid. When the electric signal changes to one for terminating the fuel injection, the spool valve operates to terminate the downstroke of the intensifier piston and instead allow control fluid to drain from the control chamber through another portion of the spool valve so that the intensifier piston can upstroke to re-charge the injection chamber with liquid fuel in preparation for the next injection.
Examples of fuel injectors having valves like those just described appear in U.S. Pat. Nos. 3,837,324; 5,460,329; 5,479,901; and 5,597,118. Some fuel injectors have a single electric actuator while others have more than one.
Commonly assigned U.S. Pat. No. 6,029,628 is an example of a fuel injector comprising two electric actuators. A supply valve mechanism is controlled by an electric supply valve actuator for selectively controlling flow of control fluid through a supply passage for downstroking an intensifier piston. A drain valve mechanism is controlled by an electric drain valve actuator for selectively controlling flow of control fluid through a drain passage. Each valve actuator is selectively operable independent of the other to selectively operate the respective valve mechanism independent of the other.
Regardless of the number of electric actuators in a fuel injector, calibration of a fuel injector is important for securing optimal engine performance. Mass production methods inherently result in some variation in calibration from fuel injector to fuel injector. While such methods may strive to minimize the range of these variations, these ranges remain significant enough that some classification of fuel injectors according to a number of different calibration categories, or groups, is believed appropriate in a mass production environment.
Hence, before it is assembled to an engine, a fuel injector is operated to ascertain its actual calibration. The actual calibration determines into which particular one of a number of different calibration categories the fuel injector falls. The fuel injector is then identified by that particular category. When an engine is being manufactured, an associated engine controller is programmed in such a way that the particular calibration category of the fuel injector for each particular engine cylinder is made available to the controller. The controller uses that data to calibrate electric control signals to the fuel injectors.
It is also known to assign a unique part number to each of the various calibration categories and to mark that part number on each fuel injector whose actual calibration falls within that calibration category. When a particular fuel injector in an engine needs to be replaced, the replacement should be one that falls within the same calibration category or else updated information should be furnished to the engine controller if a differently calibrated fuel injector is used as a replacement. A service facility may therefore have to inventory a number of different parts corresponding to the number of different calibration categories, or a controller may have to be re-programmed if a replacement fuel injector belongs to a different calibration category.
U.S. Pat. No. 5,575,264 discloses a method for associating actual performance data with a fuel injector. The data is contained in a medium that is mounted on the fuel injector body and that is suitable for reading by an associated engine controller. An EEPROM is disclosed as an example of a suitable medium.
U.S. Pat. No. 5,839,420 relates to a method for compensating a fuel injection system for fuel injector variability. Each fuel injector includes a storage medium that contains a calibration code identifying the actual calibration of the fuel injector. An associated engine controller converts a raw energizing time to a calibrated energizing time for each fuel injector based the calibration code for the fuel injector.
U.S. Pat. No. 5,634,448 relates to another method for trimming fuel injectors to compensate for fuel injector variability.
The present invention relates to improvements in identification of fuel injector calibration groups. It is believed that the invention provides certain advantages over the group identification devices and methods mentioned above. The invention may be practiced with fuel injectors having either single or multiple electric actuators. Identification of the calibration group of a fuel injector can be ascertained by an associated engine controller via all or some of the electric conductors that connect a fuel injector to an associated driver circuit. This means that no separate or additional circuit connections to a fuel injector are needed. The controller by itself can read the calibration group identification, thereby avoiding entry of that data into the controller by other means or methods.
The actual identifier for a fuel injector may comprise a passive circuit containing a conventional passive circuit element or elements, namely resistors, capacitors, or inductors, or a network containing one or more such circuit elements, or it may comprise a semi-conductor memory device such as an EEPROM. Such passive circuit elements may in certain instances be preferred because they may be less costly than semi-conductor identifiers and may not require the environmental protection that a semi-conductor device might require in order to provide acceptable service life.
Accordingly, a generic aspect of the present invention relates to a fuel injector comprising a body containing a mechanism that is operable to cause fuel to be injected out of the body and into a combustion chamber of an internal combustion engine and an electric actuator for operating the mechanism to initiate a fuel injection from the body when an initiating electric signal for initiating a fuel injection is applied to the electric actuator and to terminate the fuel injection when the electric signal changes to a terminating electric signal for terminating the fuel injection. The fuel injector also has an identity circuit that possesses a characteristic identifying a calibration category into which the fuel injector has been previously categorized and that responds to an interrogating signal in a manner disclosing the calibration category into which the fuel injector has been categorized. The identity circuit is electrically connected in shunt with the electric actuator and imposes no significant effect on the response of the fuel injector to the initiating and terminating electric signals, and the electric actuator imposes no significant effect on the response of the identity circuit to the interrogating signal.
Still another generic aspect of the present invention relates to an internal combustion engine comprising one or more electric-actuated fuel injectors each of which injects fuel into a respective combustion chamber of the engine. Each fuel injector comprises a body containing a mechanism that is operable to inject fuel out of the body and into the respective combustion chamber and an electric actuator for operating the mechanism. An electric connector on the exterior of the body contains electric terminals for connecting terminals of the actuator to an external circuit for operating the fuel injector. Each fuel injector body has a mounting on the engine that grounds the fuel injector to engine ground. Each fuel injector further comprises an identity circuit that comprises electric terminals, that possesses a characteristic identifying a calibration category into which the fuel injector has been previously categorized, and that responds to an interrogating signal applied across its terminals in a manner disclosing the calibration category into which the fuel injector has been categorized. One terminal of the identity circuit, one terminal of the electric connector, and one terminal of the actuator are connected electrically in common, and another terminal of the identity circuit is connected to engine ground through the mounting of the fuel injector on the engine.
Still another generic aspect of the present invention relates to a fuel injector comprising a body containing a mechanism that is operable to cause fuel to be injected out of the body and into a combustion chamber of an internal combustion engine and an electric actuator for operating the mechanism to initiate a fuel injection from the body when an initiating electric signal for initiating a fuel injection is applied to the electric actuator and to terminate the fuel injection when the electric signal changes to a terminating electric signal for terminating the fuel injection. The electric actuator comprises two solenoid coils that are independently actuated. The injector has an identity circuit that comprises electric terminals, that possesses a characteristic identifying a calibration category into which the fuel injector has been previously categorized, and that responds to an interrogating signal applied across its terminals in a manner disclosing the calibration category into which the fuel injector has been categorized. One terminal of the identity circuit is connected electrically to one of the coils and another terminal of the identity circuit is connected electrically to the other of the coils.
Still another generic aspect of the present invention relates to a method of identifying a calibration category of a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine wherein the fuel injector has electric terminals via which injection-initiating and injection-terminating signals are applied to an electric actuator for operating the fuel injector to initiate and terminate a fuel injection. The method comprises connecting in shunt with the electric actuator an identity circuit that possesses a characteristic identifying a calibration category into which the fuel injector has been previously categorized and that responds to an interrogating signal in a manner disclosing the calibration category into which the fuel injector has been categorized. The identity circuit imposes no significant effect on the response of the fuel injector to the initiating and terminating electric signals, and the electric actuator imposes no significant effect on the response of the identity circuit to the interrogating signal. The method further comprises connecting the electric terminals to an identifying circuit that is external to the fuel injector and causing the identifying circuit to apply an interrogating signal to the identity circuit via the electric terminals. The calibration category of the fuel injector is identified from the electrical response of the identity circuit to the interrogating signal.
Still another generic aspect of the present invention relates to a method of identifying a calibration category of a fuel injector that injects fuel into a combustion chamber of an internal combustion engine wherein the fuel injector has external electric terminals via which injection-initiating and injection-terminating signals are applied to an electric actuator for operating the fuel injector to initiate and terminate a fuel injection, and an identity circuit that comprises electric terminals, that possesses a characteristic identifying a calibration category into which the fuel injector has been previously categorized, and that responds to an interrogating signal applied across its terminals in a manner disclosing the calibration category into which the fuel injector has been categorized. The method comprises mounting the fuel injector body on an engine to establish, via the mounting, a ground between a terminal of the identity circuit and engine ground, and connecting the external electric terminals to a controller that is external to the fuel injector and that also contains an identifying circuit having first and second terminals, one of which is connected in common with engine ground. The identifying circuit applies an interrogating signal to the identity circuit via one of the external electric terminals and engine ground and identifies the calibration category of the fuel injector from the electrical response of the identity circuit to the interrogating signal.
The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows.